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OS 55 Ax Exhaust again

Old 01-18-2007, 09:46 AM
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Jag001
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Default OS 55 Ax Exhaust again

Hi Again All,

further to my last post I have just found this Tech Note

"
Posted November 20, 2006

The .55AX does not come with a 90° adapter as originally planned due to significant power loss when using such an adapter.

If you look at the adapter that's available (OSMG2590) you'll notice that the exhaust opening in the transfer is much smaller than the exhaust port on the engine (55AX) and on the muffler. The restriction causes the power loss and if made to the size required would be too large and negate the reason for its use.

The OSMG2590 adapter can be used with the 46AX and 55AX but you will notice a significant drop in performance and the Power Box muffler in the "pitts" configuration will cause other engine mounting issues.
"

The silencer adaptor I am referring to is OSMG2578, Code No 25425600 however, from what I can see of this adaptor it seems similar to the adaptor mentioned in the tech note and cause a similiar power loss problems.

cheers,

Jeff
Old 01-18-2007, 02:08 PM
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Bax
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Default RE: OS 55 Ax Exhaust again

We're not sure what you are asking here. If you need observations from a wide variety of users, you should post in the general glow forum. This forum is for questions directly to the O.S. Support staff.
Old 01-18-2007, 05:33 PM
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Jag001
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Default RE: OS 55 Ax Exhaust again

Bill,

thanks for the response, what I was trying to get at is, that the adaptor I am talking about is the the one recomended in the 55 AX engine manual as an optional accessory for this engine. I am wondering firstly if it will cause a significant loss of power if used.

Secondly I am wondering if it will cause a significant loss of power why is was it not made with a larger passage way through it. If one looks at the adaptor, the external size of the adaptor is exactly the same as the external dimensions of the original silencer mounting pad. Why would OS not have made the internal dimensions the same as the engine exhaust outler & silencer inlet.

Thirdly I am asking why the adaptor would have been manufactured with such a taper and if the taper was an intentional design feature, why would OS not indicate which way it should be fitted, via either a tech note or fitting instructions or similar.

Lastly, I have a great deal of faith in OS products and find it difficult to believe that OS has not done their homework when designing this engine, the silencer for it and the adaptors than can be used. With that said I am a modeller of some experience and have some technical knowledge when it comes to engine operation. It appears to me that restricting the exhaust outlet so close to the engine like that which would occur if this adaptor would if used could only cause engine heat problems and loss of power. That said I am no expert and therefore that is why I am asking here, would this adaptor be a problem, did OS have a reason for making such a restrictive adaptor, does the use of the adaptor detract from engine performance, or was it designed in such a way intentionally to maintain exhaust back pressure or velocity or has other positive effects that I have not thought of.

Cheers,

Jeff
Old 01-19-2007, 02:08 PM
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Bax
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Default RE: OS 55 Ax Exhaust again

Anywhere you have a restriction in the flow of exhaust gases, you have the potential for power loss. Depends upon the level of power you're trying to get. O.S. made the adaptor to fit a variety of engines and doesn't comment about how/why they made it. Total power is usually not a consideration because one of their main concerns for engines is noise.

Very likely, the extension is made the way it is for strength reasons...it must support a heavy muffler at some distance from the engine.

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